Flutter is a phenomenon encountered in flexible structures subjected to aerodynamic forces. Flutter may occur as a result of interactions between aerodynamics, stiffness, and inertial forces on a structure. In regards to a gas turbine engine, as the speed of inlet air across a fan blade, for example, increases, there may be a point at which the structural damping is insufficient to dampen the vibrational frequency which may increase due to aerodynamic energy being added to the fan blade.
Furthermore, engine inlet flow conditions may be determined by a direction of air flow relative to the fan blades. In this regard, an angle of incidence of an airfoil with respect to the direction of air flow may determine certain engine operating conditions.